> An awful lot of the things hanging in museums look "bad" to me. I'm not just talking about the easily-mocked contemporary art. I mean things like Medieval paintings with Jesus painted as a baby-sized adult man. Everything before the development of perspective looks like a grade-school cartoon.
Perspective wasn't developed! The Greeks and Romans used it just fine, for example.
What was lost was artistic training because there wasn't sufficient economic market for it. As soon as you got sufficient economic incentive, art magically improves again. This is stunningly obvious if you look at Athens and then Pompeii and then Rome and then the Vatican (with the attendant backslide until the Renaissance as you note).
Interesting parallel to modern--will AI cause a huge backslip in art since the economic market for artists is being destroyed?
"since the economic market for artists is being destroyed"
I don't see it being destroyed. I mean the market for art. That's a market for tangible things made by specific humans, pieces that are unique.
Very hard to see how AI will affect that since the market is dominated to large extent by the need by the art salespeople, art institutions, and art collectors to sustain prestige and investment value.
If it just about volume, China would have destroyed it decades ago. Clearly adding even more volume will hardly put a dent to it.